1. Field of the Invention
The present invention relates to a wavelength-conversion laser light source that includes a wavelength conversion element.
2. Description of the Related Art
A laser light source outputs a near-infrared (NIR) fundamental wave. Meanwhile, a technology for wavelength conversion to a visible wavelength to output a second harmonic (a converted wave) is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2003-270686 (page 2, FIG. 1). Japanese Laid-Open Patent Publication No. 2003-270686 describes a configuration of a fiber-pigtailed laser light source in which light output from a laser diode (LD) is input to and oscillated by a polarization maintaining fiber in which a fiber Bragg grating (FBG) is formed. The fundamental wave is converted to the converted wave by a wavelength conversion element arranged on a path for wavelength locking.
However, the conventional technology described above has a problem in that a fundamental wave that has not been converted by the wavelength conversion element is output from the polarization maintaining fiber since the polarization maintaining fiber functions as a part of an oscillator. A filter has to be provided to remove the fundamental wave from the output light, and a lens has to be further provided between the LD and the polarization maintaining fiber, thereby inhibiting size reductions. Further, the light output from the LD is coupled at many points since the light is output through multiple optical elements, thereby increasing optical loss.
To solve the problem of the conventional technology described above, an object of the present invention is to provide a small laser light source that can efficiently (with minimal loss) output a converted wave from which the component of the fundamental wave is removed.